Sort lines
Avoid leaving isodate egg around after cleaning
Remind user to push tags
Extract Python code to separate file
Assume that the correct Python version is on the path

Can be overridden by using `PYTHON=/path/to/python2.7 make`.
Releasing should depend on building, not testing
Don't call no-op `setup.py clean`

Might have done something useful before, but not anymore.
Separate development documentation
Remove generated Python files